JP2004537831A - Low pressure gas discharge lamp - Google Patents

Abstract

The present invention provides a solution to the problem that conventional electrical contacts for soldering a conductor to a metallization layer are problematic and are not suitable for mass production.
A low-pressure gas discharge lamp having a tubular discharge vessel is provided with two separate capacitive coupling members at its ends, the discharge vessel having a small inner diameter, which is preferably less than 5 mm. Each coupling member has a cylindrical tube of dielectric material. The electrical connection to the coupling member is achieved by pressing a spring element having an inner diameter smaller than the outer diameter of the cylindrical tube around the tube. The spring element forms a number of contacts by tightly surrounding the metal body on the cylindrical tube.
[Selection] Figure 2

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a low-pressure gas discharge lamp having a discharge vessel and at least two capacitively coupled structures spatially separated from one another, wherein the discharge vessel is preferably less than 5 mm. The invention relates to a low-pressure gas discharge lamp having a diameter, wherein each coupling structure is formed by a cylindrical tube of at least one dielectric material whose outer surface is provided with a metal coating. Known gas discharge lamps consist of a container having a filling gas in which a discharge takes place, and usually two metal electrodes are fixedly enclosed in this discharge container. The first electrode supplies the electrons for the discharge and these electrons are again removed to the external current circuit via the second electrode. Electrons are usually supplied by incandescent emission (hot electrodes), but instead are emitted by strong electric fields or directly by ion bombardment (ion-induced secondary emission) (cold electrodes). , Can also be generated.
[0002]
[Prior art]
In the inductive mode of operation, charge carriers are generated directly in the gas volume by a high frequency electromagnetic AC field (typically higher than 1 MHz for low pressure gas discharge lamps). The electrons travel along a closed arc in the discharge vessel, and for this mode of operation there is no conventional electrode. In the capacitive mode of operation, a capacitive coupling structure is used as an electrode. These capacitive electrodes are typically in contact with one side for gas discharge and the other side with an insulator (eg, by metal contact) connected to a conductive external current circuit. (Dielectric). When an AC voltage is applied to the capacitive electrode and the charge carriers move along the associated linear electric field, an AC electric field is formed. In the case of capacitive lamps, too, charge carriers are generated in the entire gas volume, so that in the high frequency range (f> 10 MHz), capacitive lamps are similar to inductive lamps. The surface properties of the dielectric electrode are less important in this case (so-called α-discharge mode). Capacitive lamps change their mode of operation at low frequencies and emit electrons important for discharge from the surface of the dielectric electrode to sustain the discharge, and multiply in the so-called cathode fall region. I have to do it. Therefore, the discharge action of the dielectric material is a factor that determines this lamp function (so-called γ-discharge mode).
[0003]
For many applications, it is advantageous to be able to use fluorescent lamps with small diameters (preferably 5 mm or less) and as much light as possible per unit lamp length (lumens / cm). Furthermore, in most application areas, the switching stability of the lamp needs to be high. This is especially the case, for example, for background lighting of liquid crystal displays. Hot-cathode lamps are, on the one hand, for reasons of construction and, on the other hand, for the darkening of the inner surface of the discharge vessel due to the small diameter of such lamps (and thus for a shortened lamp life). Does not meet the above conditions.
[0004]
Until recently, it has been found that fluorescent lamps with small lamp diameters (less than 5 mm) can only be realized in the form of cold-cathode lamps or in the form of capacitive gas discharge lamps with operating frequencies above 1 MHz. I was Cold-cathode lamps can be operated at low frequencies (30-50 Hz), but emit little electromagnetic radiation. However, the discharge current of such lamps is strongly limited (up to about 10 mA). One of the reasons is that when the discharge current is high, the sputtering of the electrode material is strongly increased. The other reason is that the electrodes need to be current limited in order to prevent heat emission from occurring due to local very high heating and also to excessive increase in cathode sputtering. . The electrode material removed by melting accumulates in the discharge vessel itself, which hasten the blackening of the lamp.
[0005]
For a capacitive discharge lamp with an operating frequency f> 1 MHz, a strong operating frequency and a high current density in the lamp (due to the small lamp diameter despite the high current) result in strong electromagnetic radiation. Extensive measures must be taken to limit this electromagnetic radiation. Since the power is capacitively coupled, the operating frequency is limited downward (up to about 1 MHz) by the capacitance of the coupling surface.
[0006]
European Patent Application No. 1,043,757 describes a gas discharge lamp having a capacitive coupling structure. The purpose of this patent application is to provide a gas discharge lamp with a capacitive coupling structure from a private household public power supply without using a circuit with starting electronics. This can be achieved, according to this patent application, by appropriate selection of the dielectric saturation polarization and the effective surface area of the dielectric. This patent application does not relate to gas discharge lamps, which have a preferred diameter of less than 5 mm and thus a high light output.
[0007]
In order to obtain a low-pressure gas discharge lamp with a high light output and a small diameter, preferably less than 5 mm, for the dielectric, a constant between the thickness of the dielectric and the product of the dielectric constant and the frequency Studies have shown that the ratio can be significant. Gas discharge lamps can be optimally constructed with a transparent discharge vessel with a normal filling gas and can be operated with the frequency f of the AC power source. The material of the discharge vessel and the filling gas can be selected to match the desired spectrum of the radiation to be generated. In particular, by providing a fluorescent layer in the discharge vessel, the lamp can emit radiation in a certain frequency range (eg, UV range). There are at least two mutually separated capacitive coupling structures. The dielectric can be composed of one layer or several layers. The lamp is suitable for operation with a discharge current of more than 10 mA, in which case only small amounts of electromagnetic radiation are generated. Such a gas discharge lamp can be applied to a wide range. An important application example is, for example, the case of using as background lighting of a liquid crystal display.
[0008]
The invention relates to the latter type of gas discharge lamp. However, in order to achieve practical applicability, electrical, mechanical, and thermal issues must be further resolved. In the case of the gas discharge lamp described in European Patent Application No. 1,043,757, the capacitive coupling structure formed by a cylindrical tube of dielectric material has a metallic coating (for example, silver having conductivity). Paste) is provided. A conductor is soldered to this layer for connection to an external current source. However, such electrical contacts are problematic and unsuitable for mass production.
[0009]
[Means for Solving the Problems]
It is a primary object of the present invention to provide a solution to this problem. This means that, according to the invention, the electrical connection to each coupling structure is formed by a resilient clamping element having an inner diameter smaller than the outer diameter of the cylindrical tube of dielectric material, and this resilient clamping element is Metallization of a cylindrical tube of dielectric material, so that it is made of a temperature-resistant material which can be easily soldered and / or welded and this resilient clamping element forms a number of points of contact. By clamping the end of a resilient clamping element facing away from the discharge vessel to a conductive wire by welding or soldering, while surrounding at least a part of the clamping element by a clamping force. You.
[0010]
Such contacts can be mechanically and electrically reliable and are also suitable for mass production. The resilient clamping element surrounding the dielectric coupling structure can be configured in various ways. Possible configurations include, for example, a tightening helical spring in which the contacts are provided around the metallization of a cylindrical dielectric tube and the conductors are soldered.
[0011]
In a preferred embodiment of the invention, the resilient fastening element is formed by a resilient sealing clip surrounding the coupling structure with ribs extending longitudinally of the coupling structure. The two ends are interconnected by a slotted fastening piece, while a conductive wire is fastened to the fastening piece.
[0012]
This configuration not only greatly enhances the reliability of the electrical contacts and is very suitable for mass production, but also has the advantage that the ribs of the sealing clip ensure an advantageous heat removal, thereby increasing the lamp life. Can be further obtained.
[0013]
The resilient sealing clip can be made, for example, from copper, brass, or spring steel. The clamping piece provided with the slot is preferably formed of copper or brass, to which the conductor can be easily fastened.
[0014]
The low-pressure gas discharge lamp according to the invention is very suitable for storage in a housing forming a reflector. Therefore, this lamp is very suitable for use as background lighting for liquid crystal displays.
[0015]
Thus, the reflector is formed as an elongated groove of aluminum, the end of the lamp has a coupling structure, and the sealing clip is a synthetic, electrically insulating but electrically insulating resin in the end of the reflector. It is advantageous if it is enclosed in
[0016]
Particularly good heat removal can be obtained when using a synthetic resin consisting of polyurethane filled with 50% aluminum trihydrate.
[0017]
The invention will now be described in more detail below with reference to examples which are given only by way of example.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a capacitive gas discharge lamp not provided with the measures according to the invention (this is an example and the invention is not limited thereto). The glass tube 1 functions as a discharge vessel. In addition, the glass tube 1 can be provided with a phosphor layer so that the lamp can emit radiation in the UV range. The glass tube 1 has an inner diameter of 3 mm, an outer diameter of 4 mm, a length of 40 mm, and can be filled with 50 mbar of Ar and 5 mg of Hg. The capacitive coupling structure is formed at either end by a cylindrical tube 2 of a dielectric material (eg, a ceramic oxide such as BaTiO3, SrTiO3, or PbZrO3). The dielectric cylinder 2 has an outer diameter slightly less than 3 mm, a wall thickness of 0.5 mm and a length of 14 mm. One side of the dielectric cylinder 2 is connected to the glass tube 1 by a glass melting process, and the other side is vacuum-sealed by a glass seal 3. A conductive layer (eg, a silver paste) is provided on the dielectric cylinder and contacts can be connected thereto. The lamp is connected to an external current source via the contact. The external current source of this embodiment can be formed by a lamp drive circuit that supplies a 30 mA current at 40 kHz and an average voltage of about 350 volts. The lamp in this case produces a flux of about 600 lumens during steady state operation. The drive unit further has an element for igniting the lamp. A steady gas discharge is formed after ignition.
[0019]
The gas discharge lamp shown in FIG. 1 is provided with electrical connection means. It is also preferable to pay attention to heat removal. For the lamp to be economically viable, the electrical connection and the heat removal must be suitable for mass production.
[0020]
FIG. 2 shows the end of a gas discharge lamp provided with the connecting means which is preferably used. The main point of the invention is that a resilient clamping element provided around the metal coating surrounding the cylindrical tube 2 is used for the electrical connection. The resilient element can have a variety of configurations (eg, a helical spring configuration). In the preferred embodiment shown in FIG. 2, this elastic element is formed as a sealing clip 4 surrounding the coupling structure 2 by means of a clamping force. This sealing clip has a rib 5 extending in the longitudinal direction of the cylindrical tube 2. The resilient sealing clip 4 is clamped with a clamping force around the coupling structure 2 by a clamping piece 6. The clamping piece is formed by a slotted metal piece (in FIG. 2 the widened end can be seen). This resilient sealing clip 4 is bent around the cylindrical tube 2 and the slot of the clamping piece 6 passes through the two ends of the clip in order to clamp the clip. This clip is dimensioned such that, after being clamped by the clamping piece 6, the inner diameter (the innermost end of the rib 5) is smaller than the outer diameter of the tube 2. The ribs thus make a number of contacts with the metallization around the tube 2, thereby forming a very reliable electrical connection. In this way, the conductive wire 7 can be soldered or welded to the fastening piece 6, and this wire can be connected to the current source.
[0021]
The material of the sealing clip 4 is preferably copper, brass or spring steel. The fastening piece 6 is preferably made of copper or brass because the conductive wire 7 can be easily soldered thereto. The shape of the resilient sealing clip not only provides reliable lamp contact during mass production, but the ribs 5 allow a large surface area in a relatively small space to be advantageous for heat removal.
[0022]
FIG. 3 shows the end of a reflector that can accommodate a lamp. The reflector 8 is preferably constituted by a groove-shaped aluminum part. Aluminum is highly reflective, while on the other hand it contributes strongly to heat removal. In order to fix the lamp in the groove 8, the glass tube 1 is surrounded by disks (not shown) adjoining each other joining the joint structure 2, the outer circumference of which is 8 inner wall. The ends of the grooves 8 can each be closed off by a disk (not shown).
[0023]
As shown in FIG. 4, a synthetic resin 9 of an electric insulator having heat conductivity is provided in the space between the disks located at each end of the groove. The lamp is thereby clamped in the reflector. Synthetic resins also contribute to further removing heat.
[0024]
This synthetic resin is preferably formed of polyurethane. To improve the heat removal, the polyurethane can be filled with a heat-conducting electrical insulator filler, such as, for example, aluminum trihydrate.
[0025]
The preferred embodiment of the present invention has been described above. It will be apparent that modifications are possible within the scope of the appended claims.
[Brief description of the drawings]
FIG. 1 shows a low-pressure gas discharge lamp with a capacitive coupling structure.
FIG. 2 shows the end of the lamp of FIG. 1 with an electrical connection in the form of a clamped sealing clip.
FIG. 3 shows a gas discharge lamp with a clamped sealing clip located inside the reflector.
FIG. 4 is an end of a lamp sealed in a synthetic resin inside a reflector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Glass tube 2 ... Cylindrical tube 3 ... Glass sealing 4 ... Sealing clip 5 ... Rib 6 ... Clamping piece 7 ... Wire 8 ... Reflector 9 ... Synthetic resin

Claims (8)

A low-pressure gas discharge lamp having a discharge vessel and at least two capacitively coupled structures spatially separated from one another,
The discharge vessel has a small diameter, preferably less than or equal to 5 mm,
A low-pressure gas discharge lamp, wherein each coupling structure is formed by a cylindrical tube of at least one dielectric material, the outer surface of which is provided with a metal coating,
The electrical connection to each coupling structure is formed by a resilient clamping element having an inner diameter smaller than the outer diameter of the cylindrical tube of dielectric material;
The resilient fastening element is made of a temperature-resistant material that can be easily soldered and / or welded, and
The resilient clamping element surrounds at least a portion of the metallization of the cylindrical tube of dielectric material with a clamping force to form a number of contacts;
A low-pressure gas discharge lamp, characterized in that the end of the resilient clamping element facing away from the discharge vessel is fastened to a conductive wire by welding or soldering. The resilient fastening element is formed by a resilient sealing clip surrounding the coupling structure having ribs extending longitudinally of the coupling structure;
The two ends of the sealing clip are interconnected by a slotted fastening piece,
The low pressure gas discharge lamp according to claim 1, wherein the conductive wire is fastened to the fastening piece. 3. The low-pressure gas discharge lamp according to claim 2, wherein the resilient sealing clip is made of copper or brass. 3. The low-pressure gas discharge lamp according to claim 2, wherein the resilient sealing clip is made of spring steel. The low-pressure gas discharge lamp according to claim 2, wherein the fastening piece provided with the slot is made of copper or brass. A low pressure gas discharge lamp according to any of the preceding claims, characterized in that the lamp is housed in a housing forming a reflector. The reflector is formed as an elongated slot in aluminum, and the ends of the lamp having the coupling structure and the sealing clips have a heat conducting but electrical conductivity in each end of the reflector. The low-pressure gas discharge lamp according to claim 6, wherein the lamp is sealed in a synthetic resin of an insulator. 8. The low-pressure gas discharge lamp according to claim 7, wherein the synthetic resin comprises polyurethane filled with 50% of aluminum trihydrate.

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